Chapter 22: Vertebral Column

CHAPTER OBJECTIVES

At the completion of this chapter, the reader will be able to:

1. Describe the differing anatomy of the vertebrae, ligaments, and muscles that form the various regions of the vertebral column.

2. Describe the general biomechanics of the spine, including coupled movements and kinesiology.

3. Describe the various schools of thought and approaches to spinal rehabilitation.

OVERVIEW

The design specification for the human vertebral column is the provision of structural stability affording full mobility and the protection of the spinal cord and axial neural tissues.¹ While achieving these seemingly disparate objectives, the spine also contributes to the functional requirements of gait and to the maintenance of static weight-bearing postures (see Chapter 6).¹

At the component level, the basic building block of the spine is the vertebra. The vertebra serves as the weight-bearing unit of the vertebral column, and it is well designed for this purpose. Although a solid structure would provide the vertebral body with sufficient strength, especially for static loads, it would prove too heavy and not have the necessary flexibility for dynamic load bearing.¹ Instead, the vertebral body is constructed with a strong outer layer of cortical bone and a hollow cavity, the latter of which is reinforced by vertical and horizontal struts called trabeculae.

The vertebral column describes the entire set of vertebrae, excluding the ribs, sternum, and pelvis (Fig. 22-1). The normal vertebral column comprises 29 vertebrae (7 cervical, 12 thoracic, 5 lumbar, and 5 sacral) and three or four coccygeal segments. The adage that “function follows form” is very much applicable when studying the vertebral column. Although all vertebrae have similar characteristics, each has specific details that reflect its unique function (Table 22-1). The overall contour of the normal vertebral column in the coronal plane is straight.

In contrast, the sagittal plane contour changes with development. At birth, a series of primary curves give a kyphotic posture to the whole spine. With the development of the erect posture, secondary curves develop in the cervical and lumbar spines, producing a lordosis in these regions. The curves in the spinal column provide it with increased flexibility and shock-absorbing capabilities.

Functionally, the vertebral column consists of anterior and posterior columns. The anterior column, consisting of the vertebral bodies and intervertebral disks (IVDs), is the hydraulic and weight-bearing portion that provides the vertebral column with its shock-absorbing capability. The posterior column consists of the articular processes and the zygapophyseal (facet) joints that provide the gliding mechanism for movement. A motion segment in the vertebral column is defined as two adjacent vertebrae and consists of three joints. One joint is formed between the two vertebral bodies and the IVD of the anterior column. The other two joints are formed by the articulation between the superior articular processes of the inferior vertebra and the inferior articular processes of the superior vertebra (Fig. 22-2...